Getting the pedal to be on the right spot for clipping in depends on the balance on the pedal and practice. IME Shimano system is better at that than Look at that. Speedplays were not very good at that but I’ve been told they are better now.
Getting used to it takes time and it’s easy to forget. In fact I think I’ll move to all spd for that reason in part, but mostly because I now use my road bike very sparingly.
Cleats were brand new with only 1 ride outside so they’re in great shape. The pedals are Assioma Due Shi with 105 bodies. They spin very easily and generally sit with the rear of the pedal straight down.
I have to blame skill (or lack there of!) since I’m used to SPD’s…wish I could fault the equipment 
The SPD is more of a stomp, where the SL’s are a slight toe down slide to get the pedal body level and then a stomp. Give it time, you’ll get it. I still occasionally miss a clip in, and have missed a few with the SPDs too. Speedplay pedals drove me nuts in the beginning, but I got it down. It just takes time… I still look down to clip in, for some it’s so second nature, they just hop on and CLIP and are off.
I actually find it easier to clip in with road pedals compared to SPDs; if I didn’t indulge in so much hike a bike I think I’d put SPD-SLs on my gravel bike,
I find SPD and SPD-SLs to be the same for clipping in, the main difference is if you miss on the SL the pedal starts spinning and getting it recentered can make you look a fool in a hurry.
SPD-SL - slide foot forwards on pedal body focusing on catching the toe cleat then step down.
SPD- get close and smash foot in.
I started riding SPDs some 30 years ago when I was 6, the learning curve to SLs isn’t that steep, just takes a little bit.
When I was running the bog-standard Assioma Duos, the pedal used to sit slightly past the vertical, & because of their weight balance & the smoothness of the bearings, it used to swing back & forth a lot but spend more time presenting the underside of the pedal than the top. Consequently my cleats more often found the underside of the pedal than the top. 
Now using the M-Force 8 (doublesided) bodies on the spindles, which seem to be harder to find than standard SPDs. By far my favorite pedal for clipping into was the Shimano pedals that are SPD one side, platform the other. It presents the clipless side just right. I’d still be using them if I wasn’t running a pedal-based PM.